Each source compilation generates a dependencies file. These dependencies
files are consolidated in one file per target. This consolidation is done
as part of command 'cmake -E cmake_depends` launched before evaluation of
makefile dependency graph.
The consolidation uses the same approach as `CMake` dependencies management.
Fixes: #21321
Add entries in Modules and Modules/Platform to support
Objective-C compiler determination and identification.
Add Modules to check Objective-C compiler flags, source
compilations, program checks, etc...
Use OBJC as the designator of the language, eg:
project(foo OBJC)
Add various tests for Objective-C language features. Add
tests to preserve C++ handling of .m and .mm files when
OBJC is not a configured language.
Co-Authored-By: Cristian Adam <cristian.adam@gmail.com>